bytestring-0.9.0.1: Fast, packed, strict and lazy byte arrays with a list interfaceContentsIndex
Data.ByteString.Char8
Portabilityportable
Stabilityexperimental
Maintainerdons@cse.unsw.edu.au
Contents
The ByteString type
Introducing and eliminating ByteStrings
Basic interface
Transformating ByteStrings
Reducing ByteStrings (folds)
Special folds
Building ByteStrings
Scans
Accumulating maps
Generating and unfolding ByteStrings
Substrings
Breaking strings
Breaking into many substrings
Breaking into lines and words
Predicates
Search for arbitrary substrings
Searching ByteStrings
Searching by equality
Searching with a predicate
Indexing ByteStrings
Zipping and unzipping ByteStrings
Ordered ByteStrings
Reading from ByteStrings
Low level CString conversions
Copying ByteStrings
Packing CStrings and pointers
Using ByteStrings as CStrings
I/O with ByteStrings
Standard input and output
Files
I/O with Handles
Description

Manipulate ByteStrings using Char operations. All Chars will be truncated to 8 bits. It can be expected that these functions will run at identical speeds to their Word8 equivalents in Data.ByteString.

More specifically these byte strings are taken to be in the subset of Unicode covered by code points 0-255. This covers Unicode Basic Latin, Latin-1 Supplement and C0+C1 Controls.

See:

This module is intended to be imported qualified, to avoid name clashes with Prelude functions. eg.

 import qualified Data.ByteString.Char8 as B
Synopsis
data ByteString
empty :: ByteString
singleton :: Char -> ByteString
pack :: String -> ByteString
unpack :: ByteString -> [Char]
cons :: Char -> ByteString -> ByteString
snoc :: ByteString -> Char -> ByteString
append :: ByteString -> ByteString -> ByteString
head :: ByteString -> Char
uncons :: ByteString -> Maybe (Char, ByteString)
last :: ByteString -> Char
tail :: ByteString -> ByteString
init :: ByteString -> ByteString
null :: ByteString -> Bool
length :: ByteString -> Int
map :: (Char -> Char) -> ByteString -> ByteString
reverse :: ByteString -> ByteString
intersperse :: Char -> ByteString -> ByteString
intercalate :: ByteString -> [ByteString] -> ByteString
transpose :: [ByteString] -> [ByteString]
foldl :: (a -> Char -> a) -> a -> ByteString -> a
foldl' :: (a -> Char -> a) -> a -> ByteString -> a
foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
foldr :: (Char -> a -> a) -> a -> ByteString -> a
foldr' :: (Char -> a -> a) -> a -> ByteString -> a
foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
concat :: [ByteString] -> ByteString
concatMap :: (Char -> ByteString) -> ByteString -> ByteString
any :: (Char -> Bool) -> ByteString -> Bool
all :: (Char -> Bool) -> ByteString -> Bool
maximum :: ByteString -> Char
minimum :: ByteString -> Char
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
replicate :: Int -> Char -> ByteString
unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)
take :: Int -> ByteString -> ByteString
drop :: Int -> ByteString -> ByteString
splitAt :: Int -> ByteString -> (ByteString, ByteString)
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
group :: ByteString -> [ByteString]
groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
inits :: ByteString -> [ByteString]
tails :: ByteString -> [ByteString]
split :: Char -> ByteString -> [ByteString]
splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
lines :: ByteString -> [ByteString]
words :: ByteString -> [ByteString]
unlines :: [ByteString] -> ByteString
unwords :: [ByteString] -> ByteString
isPrefixOf :: ByteString -> ByteString -> Bool
isSuffixOf :: ByteString -> ByteString -> Bool
isInfixOf :: ByteString -> ByteString -> Bool
isSubstringOf :: ByteString -> ByteString -> Bool
findSubstring :: ByteString -> ByteString -> Maybe Int
findSubstrings :: ByteString -> ByteString -> [Int]
elem :: Char -> ByteString -> Bool
notElem :: Char -> ByteString -> Bool
find :: (Char -> Bool) -> ByteString -> Maybe Char
filter :: (Char -> Bool) -> ByteString -> ByteString
index :: ByteString -> Int -> Char
elemIndex :: Char -> ByteString -> Maybe Int
elemIndices :: Char -> ByteString -> [Int]
elemIndexEnd :: Char -> ByteString -> Maybe Int
findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
findIndices :: (Char -> Bool) -> ByteString -> [Int]
count :: Char -> ByteString -> Int
zip :: ByteString -> ByteString -> [(Char, Char)]
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
unzip :: [(Char, Char)] -> (ByteString, ByteString)
sort :: ByteString -> ByteString
readInt :: ByteString -> Maybe (Int, ByteString)
readInteger :: ByteString -> Maybe (Integer, ByteString)
copy :: ByteString -> ByteString
packCString :: CString -> IO ByteString
packCStringLen :: CStringLen -> IO ByteString
useAsCString :: ByteString -> (CString -> IO a) -> IO a
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
getLine :: IO ByteString
getContents :: IO ByteString
putStr :: ByteString -> IO ()
putStrLn :: ByteString -> IO ()
interact :: (ByteString -> ByteString) -> IO ()
readFile :: FilePath -> IO ByteString
writeFile :: FilePath -> ByteString -> IO ()
appendFile :: FilePath -> ByteString -> IO ()
hGetLine :: Handle -> IO ByteString
hGetContents :: Handle -> IO ByteString
hGet :: Handle -> Int -> IO ByteString
hGetNonBlocking :: Handle -> Int -> IO ByteString
hPut :: Handle -> ByteString -> IO ()
hPutStr :: Handle -> ByteString -> IO ()
hPutStrLn :: Handle -> ByteString -> IO ()
The ByteString type
data ByteString

A space-efficient representation of a Word8 vector, supporting many efficient operations. A ByteString contains 8-bit characters only.

Instances of Eq, Ord, Read, Show, Data, Typeable

show/hide Instances
Introducing and eliminating ByteStrings
empty :: ByteString
O(1) The empty ByteString
singleton :: Char -> ByteString
O(1) Convert a Char into a ByteString
pack :: String -> ByteString

O(n) Convert a String into a ByteString

For applications with large numbers of string literals, pack can be a bottleneck.

unpack :: ByteString -> [Char]
O(n) Converts a ByteString to a String.
Basic interface
cons :: Char -> ByteString -> ByteString
O(n) cons is analogous to (:) for lists, but of different complexity, as it requires a memcpy.
snoc :: ByteString -> Char -> ByteString
O(n) Append a Char to the end of a ByteString. Similar to cons, this function performs a memcpy.
append :: ByteString -> ByteString -> ByteString
O(n) Append two ByteStrings
head :: ByteString -> Char
O(1) Extract the first element of a ByteString, which must be non-empty.
uncons :: ByteString -> Maybe (Char, ByteString)
O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.
last :: ByteString -> Char
O(1) Extract the last element of a packed string, which must be non-empty.
tail :: ByteString -> ByteString
O(1) Extract the elements after the head of a ByteString, which must be non-empty. An exception will be thrown in the case of an empty ByteString.
init :: ByteString -> ByteString
O(1) Return all the elements of a ByteString except the last one. An exception will be thrown in the case of an empty ByteString.
null :: ByteString -> Bool
O(1) Test whether a ByteString is empty.
length :: ByteString -> Int
O(1) length returns the length of a ByteString as an Int.
Transformating ByteStrings
map :: (Char -> Char) -> ByteString -> ByteString
O(n) map f xs is the ByteString obtained by applying f to each element of xs
reverse :: ByteString -> ByteString
O(n) reverse xs efficiently returns the elements of xs in reverse order.
intersperse :: Char -> ByteString -> ByteString
O(n) The intersperse function takes a Char and a ByteString and `intersperses' that Char between the elements of the ByteString. It is analogous to the intersperse function on Lists.
intercalate :: ByteString -> [ByteString] -> ByteString
O(n) The intercalate function takes a ByteString and a list of ByteStrings and concatenates the list after interspersing the first argument between each element of the list.
transpose :: [ByteString] -> [ByteString]
The transpose function transposes the rows and columns of its ByteString argument.
Reducing ByteStrings (folds)
foldl :: (a -> Char -> a) -> a -> ByteString -> a
foldl, applied to a binary operator, a starting value (typically the left-identity of the operator), and a ByteString, reduces the ByteString using the binary operator, from left to right.
foldl' :: (a -> Char -> a) -> a -> ByteString -> a
foldl is like foldl, but strict in the accumulator.
foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
foldl1 is a variant of foldl that has no starting value argument, and thus must be applied to non-empty ByteStrings.
foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
A strict version of foldl1
foldr :: (Char -> a -> a) -> a -> ByteString -> a
foldr, applied to a binary operator, a starting value (typically the right-identity of the operator), and a packed string, reduces the packed string using the binary operator, from right to left.
foldr' :: (Char -> a -> a) -> a -> ByteString -> a
foldr is a strict variant of foldr
foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
foldr1 is a variant of foldr that has no starting value argument, and thus must be applied to non-empty ByteStrings
foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
A strict variant of foldr1
Special folds
concat :: [ByteString] -> ByteString
O(n) Concatenate a list of ByteStrings.
concatMap :: (Char -> ByteString) -> ByteString -> ByteString
Map a function over a ByteString and concatenate the results
any :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a ByteString, any determines if any element of the ByteString satisfies the predicate.
all :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a ByteString, all determines if all elements of the ByteString satisfy the predicate.
maximum :: ByteString -> Char
maximum returns the maximum value from a ByteString
minimum :: ByteString -> Char
minimum returns the minimum value from a ByteString
Building ByteStrings
Scans
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString

scanl is similar to foldl, but returns a list of successive reduced values from the left:

 scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]

Note that

 last (scanl f z xs) == foldl f z xs.
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString

scanl1 is a variant of scanl that has no starting value argument:

 scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanr is the right-to-left dual of scanl.
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
scanr1 is a variant of scanr that has no starting value argument.
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
The mapAccumL function behaves like a combination of map and foldl; it applies a function to each element of a ByteString, passing an accumulating parameter from left to right, and returning a final value of this accumulator together with the new list.
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
The mapAccumR function behaves like a combination of map and foldr; it applies a function to each element of a ByteString, passing an accumulating parameter from right to left, and returning a final value of this accumulator together with the new ByteString.
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
O(n) map Char functions, provided with the index at each position
Generating and unfolding ByteStrings
replicate :: Int -> Char -> ByteString

O(n) replicate n x is a ByteString of length n with x the value of every element. The following holds:

 replicate w c = unfoldr w (\u -> Just (u,u)) c

This implemenation uses memset(3)

unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString

O(n), where n is the length of the result. The unfoldr function is analogous to the List 'unfoldr'. unfoldr builds a ByteString from a seed value. The function takes the element and returns Nothing if it is done producing the ByteString or returns Just (a,b), in which case, a is the next character in the string, and b is the seed value for further production.

Examples:

 unfoldr (\x -> if x <= '9' then Just (x, succ x) else Nothing) '0' == "0123456789"
unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)

O(n) Like unfoldr, unfoldrN builds a ByteString from a seed value. However, the length of the result is limited by the first argument to unfoldrN. This function is more efficient than unfoldr when the maximum length of the result is known.

The following equation relates unfoldrN and unfoldr:

 unfoldrN n f s == take n (unfoldr f s)
Substrings
Breaking strings
take :: Int -> ByteString -> ByteString
O(1) take n, applied to a ByteString xs, returns the prefix of xs of length n, or xs itself if n > length xs.
drop :: Int -> ByteString -> ByteString
O(1) drop n xs returns the suffix of xs after the first n elements, or [] if n > length xs.
splitAt :: Int -> ByteString -> (ByteString, ByteString)
O(1) splitAt n xs is equivalent to (take n xs, drop n xs).
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
takeWhile, applied to a predicate p and a ByteString xs, returns the longest prefix (possibly empty) of xs of elements that satisfy p.
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
dropWhile p xs returns the suffix remaining after takeWhile p xs.
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
span p xs breaks the ByteString into two segments. It is equivalent to (takeWhile p xs, dropWhile p xs)
spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)

spanEnd behaves like span but from the end of the ByteString. We have

 spanEnd (not.isSpace) "x y z" == ("x y ","z")

and

 spanEnd (not . isSpace) ps
    == 
 let (x,y) = span (not.isSpace) (reverse ps) in (reverse y, reverse x) 
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
break p is equivalent to span (not . p).
breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)

breakEnd behaves like break but from the end of the ByteString

breakEnd p == spanEnd (not.p)

group :: ByteString -> [ByteString]

The group function takes a ByteString and returns a list of ByteStrings such that the concatenation of the result is equal to the argument. Moreover, each sublist in the result contains only equal elements. For example,

 group "Mississippi" = ["M","i","ss","i","ss","i","pp","i"]

It is a special case of groupBy, which allows the programmer to supply their own equality test. It is about 40% faster than groupBy (==)

groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
The groupBy function is the non-overloaded version of group.
inits :: ByteString -> [ByteString]
O(n) Return all initial segments of the given ByteString, shortest first.
tails :: ByteString -> [ByteString]
O(n) Return all final segments of the given ByteString, longest first.
Breaking into many substrings
split :: Char -> ByteString -> [ByteString]

O(n) Break a ByteString into pieces separated by the byte argument, consuming the delimiter. I.e.

 split '\n' "a\nb\nd\ne" == ["a","b","d","e"]
 split 'a'  "aXaXaXa"    == ["","X","X","X",""]
 split 'x'  "x"          == ["",""]

and

 intercalate [c] . split c == id
 split == splitWith . (==)

As for all splitting functions in this library, this function does not copy the substrings, it just constructs new ByteStrings that are slices of the original.

splitWith :: (Char -> Bool) -> ByteString -> [ByteString]

O(n) Splits a ByteString into components delimited by separators, where the predicate returns True for a separator element. The resulting components do not contain the separators. Two adjacent separators result in an empty component in the output. eg.

 splitWith (=='a') "aabbaca" == ["","","bb","c",""]
Breaking into lines and words
lines :: ByteString -> [ByteString]
lines breaks a ByteString up into a list of ByteStrings at newline Chars. The resulting strings do not contain newlines.
words :: ByteString -> [ByteString]
words breaks a ByteString up into a list of words, which were delimited by Chars representing white space.
unlines :: [ByteString] -> ByteString
unlines is an inverse operation to lines. It joins lines, after appending a terminating newline to each.
unwords :: [ByteString] -> ByteString
The unwords function is analogous to the unlines function, on words.
Predicates
isPrefixOf :: ByteString -> ByteString -> Bool
O(n) The isPrefixOf function takes two ByteStrings and returns True iff the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> Bool

O(n) The isSuffixOf function takes two ByteStrings and returns True iff the first is a suffix of the second.

The following holds:

 isSuffixOf x y == reverse x `isPrefixOf` reverse y

However, the real implemenation uses memcmp to compare the end of the string only, with no reverse required..

isInfixOf :: ByteString -> ByteString -> Bool
Alias of isSubstringOf
isSubstringOf
:: ByteStringString to search for.
-> ByteStringString to search in.
-> Bool
Check whether one string is a substring of another. isSubstringOf p s is equivalent to not (null (findSubstrings p s)).
Search for arbitrary substrings
findSubstring
:: ByteStringString to search for.
-> ByteStringString to seach in.
-> Maybe Int
Get the first index of a substring in another string, or Nothing if the string is not found. findSubstring p s is equivalent to listToMaybe (findSubstrings p s).
findSubstrings
:: ByteStringString to search for.
-> ByteStringString to seach in.
-> [Int]
Find the indexes of all (possibly overlapping) occurances of a substring in a string. This function uses the Knuth-Morris-Pratt string matching algorithm.
Searching ByteStrings
Searching by equality
elem :: Char -> ByteString -> Bool
O(n) elem is the ByteString membership predicate. This implementation uses memchr(3).
notElem :: Char -> ByteString -> Bool
O(n) notElem is the inverse of elem
Searching with a predicate
find :: (Char -> Bool) -> ByteString -> Maybe Char
O(n) The find function takes a predicate and a ByteString, and returns the first element in matching the predicate, or Nothing if there is no such element.
filter :: (Char -> Bool) -> ByteString -> ByteString
O(n) filter, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.
Indexing ByteStrings
index :: ByteString -> Int -> Char
O(1) ByteString index (subscript) operator, starting from 0.
elemIndex :: Char -> ByteString -> Maybe Int
O(n) The elemIndex function returns the index of the first element in the given ByteString which is equal (by memchr) to the query element, or Nothing if there is no such element.
elemIndices :: Char -> ByteString -> [Int]
O(n) The elemIndices function extends elemIndex, by returning the indices of all elements equal to the query element, in ascending order.
elemIndexEnd :: Char -> ByteString -> Maybe Int

O(n) The elemIndexEnd function returns the last index of the element in the given ByteString which is equal to the query element, or Nothing if there is no such element. The following holds:

 elemIndexEnd c xs == 
 (-) (length xs - 1) `fmap` elemIndex c (reverse xs)
findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
The findIndex function takes a predicate and a ByteString and returns the index of the first element in the ByteString satisfying the predicate.
findIndices :: (Char -> Bool) -> ByteString -> [Int]
The findIndices function extends findIndex, by returning the indices of all elements satisfying the predicate, in ascending order.
count :: Char -> ByteString -> Int

count returns the number of times its argument appears in the ByteString

 count = length . elemIndices

Also

 count '\n' == length . lines

But more efficiently than using length on the intermediate list.

Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Char, Char)]
O(n) zip takes two ByteStrings and returns a list of corresponding pairs of Chars. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of unpack operations, and so space usage may be large for multi-megabyte ByteStrings
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
zipWith generalises zip by zipping with the function given as the first argument, instead of a tupling function. For example, zipWith (+) is applied to two ByteStrings to produce the list of corresponding sums.
unzip :: [(Char, Char)] -> (ByteString, ByteString)
unzip transforms a list of pairs of Chars into a pair of ByteStrings. Note that this performs two pack operations.
Ordered ByteStrings
sort :: ByteString -> ByteString
O(n) Sort a ByteString efficiently, using counting sort.
Reading from ByteStrings
readInt :: ByteString -> Maybe (Int, ByteString)
readInt reads an Int from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.
readInteger :: ByteString -> Maybe (Integer, ByteString)
readInteger reads an Integer from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.
Low level CString conversions
Copying ByteStrings
copy :: ByteString -> ByteString
O(n) Make a copy of the ByteString with its own storage. This is mainly useful to allow the rest of the data pointed to by the ByteString to be garbage collected, for example if a large string has been read in, and only a small part of it is needed in the rest of the program.
Packing CStrings and pointers
packCString :: CString -> IO ByteString
O(n). Construct a new ByteString from a CString. The resulting ByteString is an immutable copy of the original CString, and is managed on the Haskell heap. The original CString must be null terminated.
packCStringLen :: CStringLen -> IO ByteString
O(n). Construct a new ByteString from a CStringLen. The resulting ByteString is an immutable copy of the original CStringLen. The ByteString is a normal Haskell value and will be managed on the Haskell heap.
Using ByteStrings as CStrings
useAsCString :: ByteString -> (CString -> IO a) -> IO a
O(n) construction Use a ByteString with a function requiring a null-terminated CString. The CString will be freed automatically. This is a memcpy(3).
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
O(n) construction Use a ByteString with a function requiring a CStringLen. As for useAsCString this function makes a copy of the original ByteString.
I/O with ByteStrings
Standard input and output
getLine :: IO ByteString
Read a line from stdin.
getContents :: IO ByteString
getContents. Equivalent to hGetContents stdin
putStr :: ByteString -> IO ()
Write a ByteString to stdout
putStrLn :: ByteString -> IO ()
Write a ByteString to stdout, appending a newline byte
interact :: (ByteString -> ByteString) -> IO ()
The interact function takes a function of type ByteString -> ByteString as its argument. The entire input from the standard input device is passed to this function as its argument, and the resulting string is output on the standard output device. It's great for writing one line programs!
Files
readFile :: FilePath -> IO ByteString
Read an entire file strictly into a ByteString. This is far more efficient than reading the characters into a String and then using pack. It also may be more efficient than opening the file and reading it using hGet.
writeFile :: FilePath -> ByteString -> IO ()
Write a ByteString to a file.
appendFile :: FilePath -> ByteString -> IO ()
Append a ByteString to a file.
I/O with Handles
hGetLine :: Handle -> IO ByteString
Read a line from a handle
hGetContents :: Handle -> IO ByteString

Read entire handle contents into a ByteString. This function reads chunks at a time, doubling the chunksize on each read. The final buffer is then realloced to the appropriate size. For files > half of available memory, this may lead to memory exhaustion. Consider using readFile in this case.

As with hGet, the string representation in the file is assumed to be ISO-8859-1.

hGet :: Handle -> Int -> IO ByteString
Read a ByteString directly from the specified Handle. This is far more efficient than reading the characters into a String and then using pack.
hGetNonBlocking :: Handle -> Int -> IO ByteString
hGetNonBlocking is identical to hGet, except that it will never block waiting for data to become available, instead it returns only whatever data is available.
hPut :: Handle -> ByteString -> IO ()
Outputs a ByteString to the specified Handle.
hPutStr :: Handle -> ByteString -> IO ()
A synonym for hPut, for compatibility
hPutStrLn :: Handle -> ByteString -> IO ()
Write a ByteString to a handle, appending a newline byte
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